Array substrate, liquid crystal display device and manufacturing method of array substrate

ABSTRACT

The present invention discloses an array substrate, a liquid crystal display device and a manufacturing method of array substrate; an array substrate comprises a plurality of thin film transistors and a first pixel electrode connected with the drain electrode of the thin film transistor, wherein the array substrate also comprises a second pixel electrode which is arranged on the bottom of the first pixel electrode and forms mutual insulation with the first pixel electrode; The present invention can increase the penetration rate of the pixel, improve the visual color cast characteristic of a panel, and reduce uneven brightness caused by variation of electrode wire width.

RELATED APPLICATIONS

This application is the U.S. National Phase under 35 U.S.C. §371 ofInternational Application No. PCT/CN11/83431, filed on Dec. 4, 2011,disclosures of which Applications are incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to the technical field of liquid crystaldisplay, and more specially relates to an array substrate, a liquidcrystal display device and a manufacturing method of array substrate.

BACKGROUND

The liquid crystal display device comprises an LCD panel includingoppositely arranged array substrate and color filter (CF) between whichliquid crystal is filled. The array substrate is also provided with aplurality of pixel electrodes 4; the color light filter is provided witha common electrode; the obliquity of liquid crystal molecules can becontrolled by adjusting voltage between the pixel electrodes 4 and thecommon electrode to form different grey scales. A common liquid crystaldisplay has small visual angle, and the wider visual angle is obtainedby adopting the liquid crystal display modes of PVA, PVA, etc. Take PSVA(Polymer stability vertical alignment) as an example, FIG. 1 is a designof a pixel in the mode with polymer stably and vertically aligned. Inthe generally known PSVA principle, the pixel electrode 4 can be broadlydivided into four areas, and the electrode slits respectively facesdirections A, B, C, and D; when a potential difference is formed betweenthe upper and the lower panel electrodes, the pattern of power linescaused by the pixel design can roughly make the liquid crystal moleculestip in four directions; then liquid crystal molecules on the surface ofthe distribution layer are irradiated or heated for solidification andform tilt angles in four directions through liquid crystals or light orthermal reaction materials in the distribution layer.

PSVA technique in the document of the present invention refers togeneralized PSVA technique. See the following four documents forreference:

1. SID′ 04 Digest, p. 1200; PSA 2. SID′ 09Digest, p. 666; SC-PVA 3. IDW′09, p. 747; SC-PVA 4. SID′ 10 Digest, p. 595 FPA

The pixel electrode 4 of common PSVA forms a penniform shape. Only whenelectrode slit exists in the pixel electrode in the voltage applyingprocess of the PSVA manufacturing process, the arrangement of the powerline can be used to make the liquid crystal molecules broadly tip to thedesigned directions, and the liquid crystals on the surface of thedistribution layer are then heated or irradiated for solidification toform the tilt angle. However, the component in the vertical direction ofthe electric field above the electrode slit is actually smaller underbright drive, and the liquid crystal molecules cannot effectively tip insuch condition so that the electrode slit area is dimmer than theelectrode area.

In addition, the brightness or the penetration of a panel strictlydepends on the width of the slits of the pixel electrode, so that whenvariation of local slit width occurs in the manufacturing process, Murais generated on the image caused by local uneven brightness.

SUMMARY

The aim of the present invention is to provide an array substrate, aliquid crystal display device and a manufacturing method of arraysubstrate solving the problems of brightness, characteristic, and muraof a liquid crystal display device.

The purpose of the present invention is achieved by the followingtechnical schemes:

an array substrate comprises a plurality of thin film transistors and afirst pixel electrode connected with the drain electrode of the thinfilm transistor, wherein the array substrate also comprises a secondpixel electrode which is arranged on the bottom of the first pixelelectrode and forms mutual insulation with the first pixel electrode;

Preferably, said array substrate comprises a common line; the secondpixel electrode is between the first pixel electrode and the commonline; and the first pixel electrode, the second pixel electrode, and thecommon line are in mutual insulation. This is an embodiment of the arraysubstrate including a common line.

Preferably, the second pixel electrode is provided with a notch in thestacked area of the first pixel electrode and the common line so thatonly insulation materials rather than metal materials are arrangedbetween the first pixel electrode and the common line; therefore, thememory capacitance formed between the first pixel electrode and thecommon line is greater to ensure that the electric quantity of thememory capacitor is adequate to maintain crystal deflection in theinterval of two scanning cycles.

Preferably, the array substrate is provided with a plurality of recessedcontact windows; the first pixel electrode extends into the contactwindows and is electrically connected with the drain electrode of thethin film transistor. This is a specific embodiment of the connectionbetween the first pixel electrode and the drain electrode of the thinfilm transistor.

A liquid crystal display device, comprising an array substrate.

A manufacturing method of an array substrate, comprising the followingsteps:

A: forming a first passivation layer on a glass substrate;

B: forming a second pixel electrode, a second passivation layer, and afirst pixel electrode on the first passivation layer of the arraysubstrate in order.

Preferably, a common line is formed on the glass substrate before StepA. This is an embodiment of the array substrate including a common line.

Preferably, when the second pixel electrode is formed in the Step B, anotch is formed in the stacked area of the first pixel electrode and thecommon line so that only insulation materials rather than metalmaterials are arranged between the first pixel electrode and the commonline; therefore, the memory capacitance formed between the first pixelelectrode and the common line is greater to ensure that the electricquantity of the memory capacitor is adequate to maintain crystaldeflection in the interval of two scanning cycles.

Preferably, in Step B, a notch is formed in the stacked area of drainelectrodes of the first pixel electrode and the thin film transistorswhen the second passivation layer is formed, and contact windows areformed when the first pixel electrode is formed. This is a specificembodiment of the connection between the first pixel electrode and thedrain electrode of the thin film transistor without additionalprocesses, which is in favor of improving the working efficiency andreducing the cost.

The present invention adds a second pixel electrode between the firstpixel electrode and the common line; the second pixel electrode is afloating electrode, and is not electrically connected with other parts.Suppose the voltage difference between the first pixel electrode and thecommon electrode of the color filter is V1, and a potential differenceof V2 exists between the second pixel electrode and the common electrodebecause of capacitance division, so that the arrangement of the powerline still makes the liquid crystal molecule broadly tip in the designeddirections. When under actual array substrate drive, the differencebetween V1 and V2 is not much, so adding an appropriate voltage can makeboth the first pixel electrode and the second pixel electrode reach aluminance saturation point; thus, a penetration rate higher than thatobtained in a conventional mode can be obtained because the luminancedifference of the two pixel electrodes is small. When a middle greyscale is under drive, different potentials (V1 and V2) above the secondpixel electrode and the first pixel electrode are correlated withdifferent extents of liquid crystal tipping, so that the visual anglecolor deviation is improved. In addition, the liquid crystal tipping inthe present invention mainly depends on the voltage difference betweenthe first pixel electrode and the second pixel electrode so that if theeffect of the dimension difference of the electrode slits is reduced,the problem of mora is solved. In summary, the present invention canincrease the penetration rate of the pixel, improve the visual anglecolor deviation of a panel, and reduce uneven brightness caused byvariation of electrode wire width.

DESCRIPTION OF FIGURES

FIG. 1 is a schematic diagram of pixel structure in the PSVA mode.

FIG. 2 is a sectional diagram of the pixel structure of the presentinvention.

FIG. 3 is a schematic diagram of the pixel structure of the presentinvention.

FIG. 4 is an enlarged sectional diagram of the pixel structure of thepresent invention.

FIG. 5 is a sectional diagram in A-A view.

FIG. 6 is an enlarged sectional diagram of the common line area of thepixel structure of the present invention.

FIG. 7 is a sectional diagram in B-B view.

FIG. 8 is a schematic diagram of the present invention.

FIG. 9 is a broken line diagram of voltage difference of the presentinvention.

FIG. 10 is a brightness curve diagram of the present invention.

Wherein: 1, data line; 2, scanning line; 3, thin film transistor (TFT);31, first metal layer; 32 insulating layer; 33, active layer; 34, ohmiccontact layer; 35, second metal layer; 36, first passivation layer; 37second passivation layer; 4, pixel electrode; 41, common line; 42,contact window; 43, first pixel electrode; 44, second pixel electrode;45, notch.

DETAILED DESCRIPTION

The present invention is further described by figures and the preferredembodiments as follows.

As shown in FIGS. 1 to 7, a liquid crystal display device comprises anarray substrate, wherein the array substrate comprises a plurality ofthin film transistors, and a scanning line 2, a data line 1 and a pixelstructure which are connected with the gate electrode, the sourceelectrode, and the drain electrode of the thin film transistor (TFT) 3.

The thin film transistor (TFT) 3 and the pixel structure are shown inFIG. 2. The thin film transistor (TFT) 3 is on the left side, and thepixel structure is on the right side; both the thin film transistor(TFT) 3 and the pixel structure are on the same glass substrate. Thethin film transistor (TFT) 3, the first metal layer 31, the insulatinglayer 32, the active layer 33, the ohmic contact layer 34, the secondmetal layer 35, the first passivation layer 36 and the secondpassivation layer 37 are arranged on the glass substrate in order; oneside of the second metal layer 35 near the pixel structure is the drainelectrode of the thin film transistor (TFT) 3, and the other side is thesource electrode connected with the data line 1. For the pixelstructure, the common line 41, the insulating layer 32, the firstpassivation layer 36, the second pixel electrode 44, the secondpassivation layer 37 and the first pixel electrode 43 are arranged onthe glass substrate. The first pixel electrode 43 penetrates through thefirst passivation layer 36 and the second passivation layer 37, and isconnected with the drain electrode of the thin film transistor (TFT) 3so as to form the contact window 42. The second pixel electrode 44 isprovided with a notch 45 in the stacked area of the first pixelelectrode 43 and the common line 41 to increase the storage capacitance(Cst2) between the first pixel electrode 43 and the common line.

The array substrate can be made by the common lightproof covermanufacturing process at present, i. e. the above structures are formedon the glass substrate in order by the procedures of deposition,exposure, development, etching, etc. The specific steps are:

1, The first metal layer 31 and the common line 41 are formed on theglass substrate by the procedures of deposition, exposure, developmentand etching.

2, An insulating layer 32 is formed on the first metal layer 31 bydeposition.

3, The active layer 33 and the ohmic contact layer 34 are formed on theinsulating layer 32 in order by deposition, exposure, development andetching.

4, The second metal layer 35 is formed on the insulating layer 32 andthe ohmic contact layer 34 by deposition, exposure, development andetching (etching of the ohmic contact layer 34 is required in thisstep).

5, The first passivation layer 36 is formed on the surface of the wholearray substrate by deposition.

6, A first transparent conducting layer (the second pixel electrode 44)is formed on the first passivation layer 36 by deposition, exposure,development and etching, and the notch 45 is arranged in the stackedarea of the first pixel electrode 43 and the common line 41.

7, The second passivation layer 37 is formed on the surface of the wholearray substrate by deposition.

8, A contact window 42 (VIA) is formed in the position where the secondmetal layer 35 is connected with the first pixel electrode 43 bydeposition, exposure, development and etching.

9, A second transparent conducting layer is formed on the secondpassivation layer 37 by deposition, exposure, development and etching.

FIG. 8 is an equivalent circuit diagram of the pixel structure. Comparedwith the conventional circuit structure, an additional transparentconducting layer is used as the second pixel electrode 44 in the design,so that a capacitance C_(A) is formed between the second pixel electrode44 and the first pixel electrode, and a first storage capacitance (Cst1)is formed between the second pixel electrode 44 and the common line 41.

In the process of applying voltage to the PSVA liquid crystal displaydevice, if the potential difference V1 exists between the first pixelelectrode 43 and the electrode of the color filter, the capacitancebetween the first pixel electrode 43 and the electrode of the colorfilter is C_(LC2); the second pixel electrode 44 is a floating electrodebetween the common line 41 and the first pixel electrode 43; thecapacitance between the second pixel electrode 44 and the commonelectrode is C_(LC1), and the potential difference of V2 between thesecond pixel electrode 44 and the common electrode because ofcapacitance division, so V1≠V2; therefore, the arrangement of the powerline still make the liquid crystal molecules broadly tip in the designeddirection, and the tilt angle can be formed by heating or irradiatingthe liquid crystals on the surface of the distribution layer forsolidification. When under actual panel drive, if an appropriate voltageis input through the data line 1, a potential difference of Vin isformed between the second pixel electrode and the common electrode;because the potential of the second pixel electrode 44 is divided fromthe first pixel electrode, the relationship between Vin and thepotential difference (Velectrode) between the two pixel electrodes andthe common electrode is shown in FIG. 9; the brightness of the two pixelelectrode areas corresponding to V_(in) is shown in FIG. 10. Therefore,applying an appropriate voltage can make the first pixel electrode andthe second pixel electrode reach the luminance saturation point; thus, apenetration rate higher than that obtained in a conventional mode can beobtained because the luminance difference of the two pixel electrodes issmall. In addition, when a middle grey scale is under drive, differentpotentials above the second pixel electrode and the first pixelelectrode make different liquid crystal tip extents so that the visualangle color deviation is improved.

The present invention is described in detail in accordance with theabove contents with the specific preferred embodiments. However, thepresent invention is not limited to the specific embodiments. For theordinary technical personnel of the technical field of the presentinvention, on the premise of keeping the concept of the presentinvention, the technical personnel can also make simple deductions orreplacements, and all of which should be considered to belong to theprotection scope of the present invention.

I claim:
 1. An array substrate, comprising a plurality of thin filmtransistors, a first pixel electrode connected with a drain electrode ofthe thin film transistor, and a second pixel electrode which is arrangedon the bottom of the first pixel electrode and forms mutual insulationwith the first pixel electrode, wherein the second pixel electrode isnot electrically connected with other parts, the second electrodedefines a notch in a stacked area of the first pixel electrode and acommon line, and the second pixel electrode and the common line arearranged on different layers.
 2. The array substrate of the claim 1,wherein said array substrate comprises a common line; the second pixelelectrode is arranged between the first pixel electrode and the commonline; and the first pixel electrode, the second pixel electrode, and thecommon line are in mutual insulation.
 3. The array substrate of theclaim 1, wherein said array substrate is provided with a plurality ofrecessed contact windows; the first pixel electrode extends into thecontact windows and is electrically connected with the drain electrodeof the thin film transistor.
 4. A liquid crystal display device,comprising an array substrate; the array substrate comprises a pluralityof thin film transistors, a first pixel electrode connected with thedrain electrode of the thin film transistor, and a second pixelelectrode which is arranged on the bottom of the first pixel electrodeand forms mutual insulation with the first pixel electrode, wherein thesecond pixel electrode is not electrically connected with other parts,the second electrode defines a notch in a stacked area of the firstpixel electrode and a common line, and the second pixel electrode andthe common line are arranged on different layers.
 5. The liquid crystaldisplay device of the claim 4, wherein said array substrate comprises acommon line; the second pixel electrode is arranged between the firstpixel electrode and the common line; and the first pixel electrode, thesecond pixel electrode, and the common line are in mutual insulation. 6.The liquid crystal display device of the claim 4, said array substrateis provided with a plurality of recessed contact windows; the firstpixel electrode extends into the contact windows and is electricallyconnected with the drain electrode of the thin film transistor.
 7. Amanufacturing method of array substrate, comprising the following steps:A: forming a first passivation layer on a glass substrate; B: forming asecond pixel electrode, a second passivation layer, and a first pixelelectrode on the first passivation layer of the array substrate inorder, wherein the second pixel electrode is not electrically connectedwith other parts, the second electrode defines a notch in a stacked areaof the first pixel electrode and a common line, and the second pixelelectrode and the common are arranged on different layers.
 8. Themanufacturing method of the array substrate of the claim 7, wherein acommon line is formed on the glass substrate before Step A.
 9. Themanufacturing method of the array substrate of the claim 8, wherein anotch is formed in the stacked area of drain electrodes of the firstpixel electrode and the thin film transistors when the secondpassivation layer is formed, and contact windows are formed when thefirst pixel electrode is formed.
 10. The array substrate of the claim 1,wherein one second pixel electrode overlaps with the first pixelelectrode.
 11. The liquid crystal display device of the claim 4, whereinone second pixel electrode overlaps with the first pixel electrode. 12.The manufacturing method of the array substrate of the claim 7, whereinone second pixel electrode overlaps with the first pixel electrode.